text:
How can static pressure be obtained over a range of airspeeds?
Multiple instruments rely on static air pressure, i.e. pressure unaffected by airspeed.
To my understanding, no such air should exist around an aircraft. Air in motion exhibits a lower pressure measured laterally, and a higher pressure measured head-on (ram air).
Switching to an in-cabin alternate static source usually decreases measured pressure, as the cabin altitude is above outside altitude, due to its equalizing with accelerated outside air.
The only solution I could think of was to measure pressure at an angle, where both effects (Bernoulli and ram, so to speak) cancel out. Now such an angle would be airspeed-dependent. How can a reliable pressure be obtained, without computational aid, over a range of airspeeds?

Take a look at this link, I didn't read it but the first graph can help you: https://visaya.solutions/en/article/wishiknew-static-pressure-measurement

@Acsed: Thanks. Unfortunately, that image depicts how to measure dynamic vs. static pressure, while I wonder how that static pressure is obtained in the first place.

"both effects (Bernoulli and ram, so to speak)" – Those are one and the same, aren't they? The "Bernoulli effect" is the "ram effect."

Does this answer your question? Why does the faster-moving air over the static port not result in a lower static pressure?

Does this answer your question? Does the pressure at the static ports drop as the aircraft's speed increases?

@PeterDuniho: That question has responses stating that "Zero static pressure error on the fuselage exists". My question asks for how/why are these points not shifted by changes in airspeed, so I start where the other question left off. But I begin to see that this should be rather asked in a physics exchange, as it might be beyond the scope of an aviation group.

"My question asks for how/why are these points not shifted by changes in airspeed" -- i.e. you start with a false premise and ask why it should be so. That's not a useful question. The duplicates both rebut your premise and go on to explain how real airplanes deal with the actual effects of airspeed on static pressure. That's the best you can hope for, when you ask the wrong question.

I used to have that misconception too.
It turns out, to get that pressure drop, you need to accelerate the air. On aircraft, this is done by changing its direction and causing it to flow around convex curvature. This occurs at the tail, on top of the wings, and often at subsonic speeds, on the nose just past the tip high pressure point, and beneath the wings. (Yes, subsonic flow is weird)
Freestream air flowing undisturbed past a flat surface will have the same static pressure - relative to the surface or absolute -, regardless of airspeed.

Thanks for your answer! "Freestream air flowing undisturbed past a flat surface will have the same static pressure": How does that relate to a straw sticking together when air as blown through? (Or my shower curtain hugging me)? In both cases, it seems that a constant flow is present.

You will find sources that tell you that it's because fast air simply has low pressure. But the truth is this: fast fluid drags slow fluid, which drops in pressure. This pressure drop is more intense when confined, so fluid jet is attracted to surfaces

Airspeed indicators on older aircraft are often directly connected to static and pitot pressure through tubing that runs to the static ports and pitot probes.
Those indicators pretty much indicate the difference between the pitot pressure and static pressures. That type of indicator shows Indicated Airspeed.
Calibrated Airspeed is generally Indicated Airspeed corrected for instrument, installation, position, and configuration errors due to incorrect air pressure at the static port.
Aircraft Operating Handbooks for older aircraft often provide tables for determining Calibrated Airspeed at different speeds and configurations, (like flap extension) if pressure at the static ports are significantly affected.

True Airspeed is Calibrated Airspeed adjusted for temperature.
Modern aircraft have static ports and pitot tubes connected to an air data computer that also get inputs from other aircraft sensors (like air temp, and flap/slat extension) to accurately indicate a True Airspeed that is calibrated specifically for the the aircraft.
I've answered this as these terms relate to aviation because it's an aviation group. If the interest is a more general instrumentation and measurement oriented, maybe a company like Omega still has instrumentation handbooks online. A good avionics text book will walk you through the principles and calculations too.

This would explain how any remaining pressure change is accounted for, even after placing the port on a suitable location


text:
Are warnings generally "source-focused" or "effect-focused"?
I have trouble wording this question, please bear with me.
Sullenberger recently stated that the pilots of the fatal MAX flights where likely under sensory overload caused by "multiple, compounded alerts". Which makes me wonder: As a general rule of thumb in modern commercial aviation, do we try to alert pilots of the cause of an issue (this or that part is out of order, e.g. we lost a hydraulic pump), or of the effect (we cannot move the control surface anymore)?

Only alerting of the cause might make them overlook effects.
Only alerting of effects might take away a chance to solve/remedy the issue.
Alerting of both might be the overload mentioned before.

Or is there another system in place, like filtering or at least ordering warnings by severity? I am a software architect by trade, and we always go with "display the error in the earliest possible step, and ignore the rest." The rational is: Do not distract me with the facts that my paint job is getting blisters and my tires are flat, if we already determined that the car is on fire.

John K's answer is great for older designs like the Boeing 737. You specifically mentioned the 737 MAX crashes, which (despite being quite a new design) still uses the old cockpit alert philosophy based on the 1960s design of the first 737. Things have however changed a bit since then.
Both Airbus and Boeing have developed systems that come a bit closer to what you call "effect-focused". They will still tell you the source of the problem, but also provide a solution and list important effects.
Airbus calls this the ECAM (Electronic Centralized Aircraft Monitor). Here is an example from an A380:

(Airbus A380 FCOM - Indicating/Recording - ECAM - System Description)
On the left you can see the Caution message in amber (in this example, a low pressure in the green and yellow hydraulic systems). The checklist directly below is what the pilots would go through as a result of this failure. This is equivalent to looking this checklist up in the paper QRH, but having it on screen is faster and you can't accidentally go through the wrong checklist. Below the checklist, there are some effects (in this case: the pilots should be aware that the slats will extend more slowly) and limitations (here maximum airspeed of 200 kt) shown. After working through the checklist, the screen on the right would be shown with more limitations for the different phases of flight.
Boeing uses a similar system called EICAS (Engine Indication and Crew Alerting System) on their newer designs (747 since the -400, 777 and 787; I think also 757/767 after avionics upgrade). The 737 (including the MAX) is not equipped with EICAS. Here is an example from the Boeing 777:

(Boeing 777 FCOMv2 10.50.4 - Flight Instruments, Displays - Electronic Checklist Displays)
You can see a similar caution message in amber at the top (for low hydraulic pressure in the center system). Below is a description of the problem and an interactive checklist to go through. At the bottom you find a list of inoperative items affected by this failure.

His question is about whether the message itself relates to the root event or the potential final result of the event. The newer ECAM and EICAS systems just present the QRH data along with the message electronically, which still doesn't really get into whether the message describes the potential final result.

@JohnK The caution/warning message is still about the root event, sure. But you can see some effects from this failure (like SLAT SLOW in the A380 example) under the checklists. These probably also appear in the QRH. I think this is exactly what OP wanted to know.

Yes, whatever's on the display will be what is in the QRH and there is likely still a paper QRH on board as a backup.  What the OP wanted to know is whether the warning itself referred to the precise failure parameter, or referred to the ramifications of the failure, is how I interpreted it.  In any case, all the bases are covered I'd say.

They are source focused. They display precisely the condition that exists, not the follow-on effects.
WARNING indications that could be dangerous if not acted on right away are Red.  Indications that must be taken into account with some action but are not an immediate danger are called CAUTIONS, and are Yellow.  Indications that just indicate a status condition, like a loss of redundancy which does not degrade function but needs to be addressed on the ground, are Status messages, and are White.
Most indications are just exceedances of some parameter above or below a limit, like an idiot light on your car.
Examples:
"GEAR BAY OVERHEAT" would be a red WARNING that tells you that the temperature in the landing gear bay exceeded a certain temperature.  Not necessarily that there is a fire.
"L ENG LOW OIL PRESS" would be a red WARNING that tells you the oil pressure dropped below x psi.  Not that the engine is about to blow up from lack of lubrication.
"R SCAVENGE EJECTOR" would be a yellow CAUTION indicating that the output pressure of the scavenge pump in the right fuel tank is below X psi. As a Caution, it needs to be acted on in some way, but it's not a danger right now.
The protocol is, a message tells the pilot exactly what condition was exceeded or what failed.  What to do about it is found in the Quick Reference Handbook that is usually stowed at the base of the center console where both pilots can reach it.  It's a binder with a tall narrow page format, with all of the  Caution and Warning messages cataloged by system, and a logic flow chart presentation for each with a procedure for each CAUTION and WARNING that is to be followed, that is meant to be easy to follow in a dark cockpit while under stress.
Only a small number of WARNING conditions expect the pilot to deal with the condition from memory.  These are called "Memory Items" or "Immediate Action Items", and you're expected to be proficient and doing steps A B C D immediately from memory.  The QRH is consulted later to perform an expanded procedure when safe to do so. There might be half a dozen or a dozen WARNINGs that have memory items that need to be performed as soon as the warning appears, and you have to have nailed down in your mind so your hands just fly around automatically when they happen.
For example, an engine fire on takeoff has a series of Memory Items, done as a standardized drill: thrust lever to idle (with a protocol where each crew cross checks and confirms the actions), thrust lever to fuel shutoff, Fuel and Hydraulic Shutoff button push, Fuel boost pump off, Fire Extinguisher Push if the fire indication hasn't gone out, and so on.  For  that sort of thing, you drill those sequences until you're blue in the face and can perform the steps without having to think about them, while under intense pressure and distraction.
Another one would be a depressurization event.  After the crew gets their masks on and establishes communication with each other through the mask mics, you declare "emergency descent", slam the thrust levers to idle, pop flight spoilers fully out, dial the autopilot altitude select to 10000 ft, engage autopilot speed mode, causing the plane to pitch over to maintain the speed with the thrust removed, and dial the speed setting to maximum operating speed (Vmo).  Those are the memory items. Once settled down in the descent with the autopilot holding the airplane in a shallow dive at redline speed (if you think something structurally is compromised after a "big bang", company procedures may advise staying at current airspeed in the dive instead of accelerating to Vmo), the non-flying pilot gets out the QRH and you go through the expanded depressurization procedure together.
Messages will generally be prioritized when multiple messages appear, and lesser importance ones filtered out when a lot of conditions are set. And a lot of messages are inhibited during the takeoff process because they can wait.
WARNING messages will often be accompanied by CAUTIONS, but multiple WARNINGS are unusual.  Getting multiple WARNINGS in a situation where you are already surprised by seemingly nonsensical activity (like trim wheels spinning madly for no apparent reason) can push you toward brain lock unless you've trained yourself, or have the right instincts. Boeing thought that the trim wheel spinning madly for no reason could be dealt with using the Stab Trim Runaway procedure, but stab trim runaways don't generally include the trim running wildly, then stopping, then starting again, then stopping again.
At some point you have to just ignore all the data and just fly the plane.  But that's pretty tough when the plane is trying to dive itself into the ground seemly possessed by a demon, in addition to all the garbage being presented as messages.  It's not hard to imagine anybody going into brain lock with that kind of data explosion combined with bizarre behaviour.

Thank you for response and all the effort it must have taken.

For current guidance refer to AC 25.1322-1 Flightcrew Alerting. With the B787, the FAA applied Special Conditions to improve crew alerting. The result of the B787 certification was an update to 14 CFR §25.1322 and the creation of the AC.

No worries I was in the industry many years both on the flying side and product development/support side. Didn't take long to write.

Didn't you forget the very first, and most important, item (or three, actually) for depressurization?

If you're talking about dialing 7700, calling the Mayday and announcing to the cabin, those aren't IAIs.

@JohnK I think Jan Hudec meant the oxygen mask.

Well I was specifically referring to the steps to configure the airplane itself, but I take your point and made an edit.  Thanks

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

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Are NPRMs published in the Federal Register?
Are FAA NPRMs (Notices of Proposed Rulemaking) published in the Federal Register?
I am currently researching the history of some airspace rule changes from the early 1990's, and am trying to figure out whether searching the Federal Register will turn up NPRMs, or only the resulting Final Rules.
For instance a "Terminal Airspace Reconfiguration NPRM", which is referenced on page 38963 of the Federal Register Volume 57 # 167 (Thursday August 27 1992).

Since posting my question, I've learned that the answer is "yes".  For example, the following URL opens to a FAA NPRM published in the Federal Register: https://www.federalregister.gov/citation/57-FR-18954

Truth is this whole question was kind of a brain fart, over the past several years I have located several NPRMs in the Federal Register, but then I just forgot.

@ymb1 -  comments cleared

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Can we see evidence of "crabbing" when viewing contrails?
Can we see evidence of "crabbing" when viewing an aircraft leaving a contrail?
Such as, in the form of an angular misalignment between the longitudinal axis of the aircraft (i.e. the aircraft centerline) and the contrail?
Or any other way?
If not, why not?  Do aircraft flying up at the contrail altitudes simply avoid crabbing?

Yes, you can see evidence, but it isn't the angular misalignment you are picturing...
The aircraft does not crab relative to the airmass, it crabs relative to the earth.  So, you will never see the contrail angled away from the aircraft's longitudinal axis.  What you will see instead is the contrail drifting.
Observe the time lapse video linked below.  You will see several aircraft starting at the top of the screen, traveling towards the bottom.  The "wind" in this case is coming from the left, and the contrails drift off to the right.
Contrail Time Lapse Video Link
Each airplane is following the same ground track, and is crabbing some amount to the left in order to maintain the centerline of what is probably an airway.  However, the contrails remain aligned with their fuselage and path through the airmass as they drift.

Crabbing is the misalignment of the aircraft's longitudinal axis with the direction of travel over ground, caused by crosswind.
The crabbing cannot be seen by looking at the angle at which the contrail is trailing behind the aircraft; both the aircraft and the contrail are offset by the wind by the same amount.

I'm being a little pedantic, but if an aircraft has an issue, such as loss of an engine on one side, then it will tend not to fly straight, and this will, in theory mean that there will be an angle between the plane and the contrails.

@MikeB but that's not called crabbing, that's called a sideslip.

The crabbing is evidenced by the drift of the contrail as the plane passes. Think about it.
Imagine you are crossing a river. Because of the current, you point upstream to track straight across. Your wake trails out straight behind you. If you're a crayfish sitting on the bottom, you look up and see a boat pointed upstream but actually traveling straight across the river. The boat's wake will drift downstream as you watch it. Same thing, except moving air instead of water.

@JohnK I took the liberty to include your comment into the answer, in the hope that this answer will finally disappear of our mod-dashboard ;-)

I've had experienced rivermen tell me that the reason they point the bow sideways to the current when "ferrying" across is so that the current will push the boat across the river, i.e. exert a force on the up-current side of the boat.  Is there no end to the ways that humans can be deceived?

The boat is basically gliding on a water "thermal" going sideways down a trench, instead of up.

I feel this answer can be improved with references linking crabs and crayfish as crustaceans, thereby enhancing our understanding of the ground track  concept.

@RobertDiGiovanni ROFL


text:
Does ARINC 825 (Aviation CAN bus) follow the same protocol as automotive CAN buses?
From what I can gather it is derived from the automotive industry standard CAN (Controller Area Network) bus, but I was wondering if they share the same protocols. If you took an automotive bus reader and hooked it up to a ARINC 825 system would it read the same?

It would be able to determine IDs of responding devices but likely not much functional or useful information as ARINC also defines an application layer protocol, there is rarely in the wild "naked can" implementations, CAN on its own does not really define semantic meaning of data transfered back and forth by the CAN bus. Your automotive reader supports automotive applications, if one is similiar enough to arinc you might get intelligible data

Yes, the underlying CAN protocol is the same.  The 825 standard specifies some CAN IDs/priority scheme for standard purposes, similar to the ARINC429 label standard.  It also specifies certain CAN bit timing configuration, such as 1 sample per bit at 75% of the bit time, and re-synchronization jump width at 1 time quanta.  These are all settings in the CAN standard.
This datasheet provides some hints, but unfortunately being an ARINC standard there isn't much public information about the label and data structures.
Holt HI-3110 ARINC 825 compatible transceiver
If you connect a CANBus tool that supports extended ID's you should be able to see the CAN data.  The bus is comparable at a CANbus and electrical level.


text:
Is there standard ticket data format specification for commercial flight operators?
I am new to this group and what brings me here is I am doing a research on ticketing solutions for commercial airlines. So I just wanted to find out if there's a international standard specification for data exchange between ticketing solutions and where can I find it (if it exists) ?
By specification I am referring to data fields and sizes that should be captured on a ticketing system like PNR, departure/destination, datetime & airport, ticket number & cost, no shows, etc

Welcome to aviation.SE! If you don't get a good answer here you might try asking on travel.SE. Ticketing and pricing aren't always an aviation issue although they're certainly closely related.

IATA does have a standard for Boarding Pass Bar Codes that outlines a lot of encoding information and other things. This holds so long as you are not showing up to a Cuban airport in your own plane. There are lots of numbers and codes on boarding passes that mean all kinds of things. Ticketing systems may contain even more information than the boarding pass its self and that is up to the implementation of the system. The effective minimum set of identifying information is likely to be (more or less):

Departure airport code
Arrival airport code
Departure time typically a local time although most aviation things run on Zulu time in practice.
Seat number
Flight number (code share possible)
Date of flight
Passenger Name
Record Locator (Some kind of ID for the information)


text:
What are the "Static Ports" in a Boeing 767?
Recently while I was on a flight, I've noticed this area near the front door on a Boeing 767 aircraft. I'm a total aviation noob, I just wonder what are these and what they are used for.

This is what can happen if the static ports get blocked.

related, if not duplicate: https://aviation.stackexchange.com/q/17440/1467

There's already a detailed description at Wikipedia.

@DavidRicherby and you know we don't send people to wikipedia to look for answers

Possible duplicate of How does a pitot plate work?

@Matt - another user has already suggested that three comments above. Also - that question seems  to be about the differences between the Pitot Plate to the Pitot Tube. Here I'm asking what are Static Ports.

@unfa The duplication is because Matt's comment was added automatically by the system.

@Federico The SE sites I spend most of my time on feel that it's not a productive use of anybody's time to write SE answers to just duplicate Wikipedia in a way that's less detailed and more likely to go out of date. I'll try to remember that Aviation doesn't see thing that way.

What's wrong with giving a short concise answer with a reference to the more detailed Wikipedia article?

@bogl - Maybe it's because articles on outside sources might change or disappear in the future. That's a guess though.

One of the standard instruments of an aircraft is a "Pitot tube". This instrument allows measurement of the forward air pressure as the aircraft moves through the air. By this measurement the instrument can estimate the relative air speed of the aircraft.
In order to make the measurement, the forward air pressure is compared to the side air pressure and the difference between the two is presumed to be due to the force of the aircraft moving through the air. Thus, the measurement is a relative one, comparing the forward air pressure to the air pressure on the side of the plane.
The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much as compared to the pitot tube which takes in air as the plane rushes through it, thus frequently changing according to the speed of the plane. The pitot tube is usually located on the bottom of the plane and is pointed forwards.

In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle); you're correct however, that the difference between the "ram air" pressure at the pitot port and the velocity-reduced pressure at the static port gives IAS.

Why are there there separate Static Ports for the Captain and First Officer?

@unfa Almost all instruments exist at least twice for redundancy. They are either manually (by the pilots) or automatically (by some computer) cross-checked against each other. That way, if one of them fails, you can still use the other to fly the plane.

And the standby / backup system typically has its own inputs as well

"In fact, the pressure at the static ports will drop as the aircraft's speed increases" - I'm not so sure about this, so I posted a question asking about it: https://aviation.stackexchange.com/questions/56631/does-the-pressure-at-the-static-ports-drop-as-the-aircrafts-speed-increases

You should probably also mention that the static ports are essential for the altimeters and variometers.

The airplane instruments that need barometric data, airspeed, altitude, vertical rate and all that, need to have a connection to the atmosphere that reads the true ambient air pressure unaffected by the dynamic factors going on in the air stream.  You can't measure the air in the pressure hull for obvious reasons, and you can't just measure the pressure in an unpressurized part of the fuselage because there is usually some amount of ram or suction influence on the air within that space and it can't be relied upon as a true indication.
The only place where you can measure true ambient (or static atmospheric) pressure on a body moving through the air at high speed is with a hole that is flush to the surface and perpendicular to the airflow.  That's what the static port is.  It's always along the side where the surface is more or less perpendicular to the air stream, and is usually near the front where the equipment that needs to measure the ambient pressure resides.  Hence the static ports just aft of the cockpit beyond the curve of the nose.


text:
Why are liquids deemed hazardous in airport security?
Airports seem to have strict rules for the amount of liquids the passengers are allowed to take on a plane.
Why is that so?

Expect that your lacking knowledge of Die Hard 3 is serious, please use common sense before asking trivial questions: http://lmgtfy.com/?q=why+liquid+restrictions+at+airports

It is in part due to the 2006 transatlantic aircraft plot, a plan to use explosives disguised as soft drinks to bring down a series of airplanes. As for how they chose the 3 oz. 1 Liter bag rule:

In an interview, Mr. Hawley explained that security officials in the
  United States, Britain and elsewhere quickly determined that the
  liquids explosion plot was “chillingly real.”
In August 2006, the thwarted terrorists were planning to use “a
  formulation that was specifically put together to get around our
  screening measures,”
...
Tests showed that a container of a certain size is needed for an
  effective explosion. Separate three-ounce containers limited in number
  to what will fit inside a single one-quart bag do not have “enough
  critical diameter” to blow up an aircraft, he said.

This is similar to why you also now need to put your shoes through the X-Ray Machine.


text:
Is there a global map of aviation waypoints?
Is there such a map or database available to the public?

I doubt there is a globally-maintained map. The closest you can get is Navigraph's (and other similar services) database, or "local" maps maintained by individual FIRs.

There's no one authority that maintains a global database. You have to rely on a service that consolidates the data from the various authorities. I often refer to Skyvector.

Thanks for the info. Cheers.

I think what you are searching for is SkyVector
Its a web-map where you can see waypoints, NDBS, DMES, FREQUENCIES, ETC

Each country publishes an AIP that, among many other things, lists all their waypoints and coordinates. Note that an AIP is formatted as a written document, not as a database. Some also publish databases, but they each use a different format and may require payment to access.
There are commercial services that collect all these databases (or parse the AIPs if needed), convert them into a common format and merge them into a single database—and repeat that process every time any country releases updates to their AIP. Obviously, that's a lot of work, so nobody is doing it for free.


text:
What is CAS and EAS and how to calculate from IAS?
I am trying to understand IAS, CAS, EAS, and TAS. I was under the impression that CAS is IAS corrected for instrumentation error and position error. The error is specific to the type of aircraft. Why then on the wikipedia page for CAS is there a formula to calculate CAS which is a function of just dynamic pressure? Where did this formula come from and how can it be valid if the correction for CAS is aircraft specific?
Also, EAS is CAS corrected for compressibility. What does this really mean? How can I convert a speed in CAS to EAS?

Interesting article but I still don’t get how CAS can be calculated based solely on impact pressure like the Wikipedia article suggests. Where did this formula come from? The article you linked says the error becomes greater with higher angle of attack yet angle of attack is not a term in the equation?

How? By definition. "CAS is defined as a function of impact pressure alone". This is the value, the truth, that we want to measure. But given imperfect instruments, we can only get IAS. From there, we can use all our engineering knowledge, lab testing with more accurate instruments, etc, to get correction tables from measured IAS to the true CAS. They can be as complicated as you'd bear, but their sole aim is to arrive at a simple (but theoretical) truth.

If you don´t mind, I´ll keep it in simple terms.
We start off with IAS - that´s the airspeed you see on your instruments. You have static port - registering pressure around your aircraft, pitot tube, registering how many molecules of air getting inside. And by subtracting one from another, you get your IAS.
Dummy example: Static registers 100 molecules around. Pitot registers 200 molecules, which would equal to speed of 100kts.
CAS - it the speed corrected for instrument error. Because no instruments are perfect.
Again, just one example, since a/c is moving through the air, pushing the air aside, it does create lower pressure around the a/c. Which in term, does affect reading of static and pitot tubes (registering wrong amount of molecules).
As a pilot, CAS is less relevant speed, as it will be used mostly for certification process.
CAS - EAS is made by allowing for compressibility effects. At very high altitude and very high speeds (jet fighters/bombers/space shuttle), there are different rules in action.
There is another speed, TAS. If you want to do everything perfect, first you need to convert IAS to CAS, (by using special table for a given airplane) and then convert CAS to TAS.
TAS is your real airspeed, moving through the air. It might differ greatly from IAS depending on pressure and temperature. In standard (ISA) conditions CAS will be equal to TAS.
But what happens when you fly at an altitude of 40.000 feet? Well, air is a lot less dense. For a given cube of air, there are a lot less molecules.
In order to fly and not to stall, you must see "100kts IAS" on your airspeed indicator. Ssince there are so fewer molecules in the air, your real airspeed through the air must be 2-3 times higher, in order to hit all those 100 molecules. Does it make sense?
As a pilot, greatest importance for you is IAS. It shows you how many molecules of air you are hitting (dynamic pressure). Stall speed, never exceed - all based on IAS. Your TAS can be whatever, but IAS is the one affects your airplane.
So why do we care about TAS? Well, based on TAS and wind, we can derive our GS - ground speed. And GS is important! It will tell you, how long time will it take for you to get from A to B. Based on time, you know how much fuel you will need. Perhaps, you would need to make an extra refuelling stop on your way. Or you calculate and see that airport will be closed by the time you arrive there?
Later on, as an airline pilot, you know if you are early/late, duty times, etc, etc.
There is Mach number as well, but since you didn´t ask, I´ll just say you will need it flying at higher altitudes (approx. above 25,000 feet) and at those altitudes, it will take over IAS.

Thanks I appreciate your response. Like you said, I have heard there are tables to convert IAS to CAS for a given aircraft. Now the Wikipedia article I linked gives an equation to calculate CAS based on dynamic pressure but how can CAS only depend on dynamic pressure and not anything else? Then all conversion tables from IAS to CAS would be the same and not dependent on the type of aircraft.

Perhaps if you think of it this way: there is no instrument on board the aircraft that can give a direct measurement of dynamic pressure. The only thing you get is IAS, which you can then convert to CAS using the correction tables from the flight manual. Now you can calculate dynamic pressure.

continued comment ... by using the Wikipedia formula you quote to solve for Qc (dynamic pressure).
You would theoretically need Qc to calculate Mach number from CAS if flying at supersonic speed. Theoretically, because in practice these aircraft will have a Machmeter that will do this mechanically for the pilot. (or an air data computer, which knows these formulas).


text:
Constant Speed Prop Power Settings
I'm studying the performance data for a Piper Arrow with a constant speed propeller. The rule of thumb that I've heard is not to let manifold pressure go above RPM. This performance data seems to show some configurations where this doesn't hold true. Am I reading the table correctly? And is the rule of thumb not true in this case?

For example I read the 23.7, 23.4, 23.0 etc. as MP under the RPM of 2200, under 55% power column. Is that wrong?

@MichaelHall see my clarification

Oh yeah, I wasn't interpreting it correctly...  Thx.

@Chris It does thanks. I was also specifically interested in whether I was reading the performance chart the correct way, which that question doesn't answer directly but it seems more obvious that I am now.


text:
Navaid information on SID
I noticed this information under the navaid boxes on the Logan Four departure from KBOS. What do they mean? Additionally could you point me to what publication they would be explained in?

Those are the low- and high-altitude enroute charts where you find Boston VOR.
There is a PDF document called Legends & General Information that is found on the bottom of the terminal procedures website from the FAA.
https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dtpp/search/

L-34 Chart
https://skyvector.com/?ll=42.34991942247282,-70.99089362657521&chart=434&zoom=3

L33 Chart
https://skyvector.com/?ll=42.349950457479316,-70.99094187247229&chart=433&zoom=3

And just for SA, those enroute chart references and the lat/long coordinates are going away.

https://www.faa.gov/air_traffic/flight_info/aeronav/acf/media/RDs/22-01-371_Enroute_Refs_Coordinates_on_DPs_STARs.pdf


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Holding with no radial specified
During my instrument check ride a couple years ago I was given an unpublished hold by ATC at a fix in the approach. For the hold ATC said something to the effect of "... hold west of [fix name] ..." with no radial, course etc. to hold on specified (at least that's the way I remember it from the check ride...I could be misremembering). Ultimately the hold was cancelled before we got there so I was bailed out from my confusion. However, my question is: am I remembering the instructions right? Will ATC give a hold with no course specified? And if so, what is the expected course?

From FAA Order 7110.65AA:

4−6−4. HOLDING INSTRUCTIONS
When issuing holding instructions, specify:
a. Direction of holding from the fix/waypoint.
b. Holding fix or waypoint.
NOTE−
The holding fix may be omitted if included at the beginning of the transmission as the clearance limit.
c. Radial, course, bearing, track, azimuth, airway, or route on which the aircraft is to hold.
[...]

So this information is required.
It does say elsewhere that this can be omitted if it is a published hold. Even then, it instructs ATC to give full directions at pilot request. You can and should (and must, per 14 CFR § 91.123(a)) ask for clarification any time you are uncertain of an ATC clearance.

Thanks. I probably missed the course in his instructions then.

@Tom That or an ATC mistake, or the hold was published and you didn't realize it, I suppose.

Sadly, "published" doesn't always mean "published on the chart I'm looking at right now". A holding pattern published for a fix on a low chart might not always show up on a high chart or on an approach chart, or vice versa. Databases tend to help in that regard, but you're still left with needing to confirm what the database pulled up.


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How to compute actuator torque requirement for Variable pitch mechanism??
Suggest me any reference to compute the torque requirement for actuator/motor to control the pitch angle of propeller (Variable Pitch Propeller).
Thanks in advance
Arun Ravindran

Welcome to the site @ArunRavindran. This sounds like a homework question, and it's a bit vague to be honest. what have you looked at already?

Most variable pitch propellers are controlled by a combination oil pressure, counterweights and springs.  I am not aware of any that use an actuator or motor to control pitch.  If you do a Google search you will find lots of graphics and tutorials explaining how they work.

Thanks for the advise. We are currently working on design of large UAV class platform. I have came across few techniques where people have used servo/motor to control the pitch angle (beta) variation during their flight to attain optimum efficiency throughout the flight envelop. Please verify Summary of Propeller design procedure and data Vol III - they have given brief explanation about actuator based variable pitch mechanism. Even they have given the calculation for centrifugal twisting moment (torque required to change the beta angle).

Problem is they have used a constant value without any reference. Kindly suggest me any reference or method to compute the torque required to change the beta angle of blade. Thank you once again.


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After the phugoid mode subsides, in the steady state, why is there a small increase instead of decrease in the flight path angle?
In the book Dynamics of Flight, I came across the following statement in Chapter 7, Section 7.7: Response to elevator

The flight path angle is seen to be almost unchanged - it increased by about one-tenth of a degree. The reason for an increase instead of the decrease that would be expected in normal cruising flight is that at this flight condition the airplane is flying below its minimum-drag speed.

The above statement is actually explaining the below scenario: the phugoid mode response when elevator  displacement is one degree down.

Q. I know that

As shown in the blockquote statement, if the airplane is flying below its minimum-drag speed then drag will be high (referring to the power curve), resulting a decrease in the flight path angle  negative. Then why is the book mentioning an increase in the flight path angle. Please correct my chain of thought.
Thank you!

Please put your answers in answer, and use comments for clarifications.

Before the step change of the elevator the aircraft was in quasi-static stable flight: flying at a constant horizontal flight path angle ($\gamma = 0$) and no logitudinal acceleration.
After the step input on the elevator (1 degree down) is applied, the phugoid starts and slowly decays towards the new static equilibrium.

The new elevator position causes a pitch down moment.

Since the aircraft is longitudinally stable, the aircraft tends to pitch up at higher speeds.

The new static equilibrium is thus found at a higher speed, such that the pitch down moment from the new elevator position is compensated for by the pitching up moment from the higher speed.

Since the orginal equilibrium was at a speed below the minimum drag speed, at the new (higher) speed, the drag will be lower. Assuming the engine provides the same thrust at the higher speed, the flight path angle
$$\gamma = \sin^{-1}\left(\frac{T-D}{W}\right)$$
will now be positive, because the term $(T-D)$ is now positive.


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How is an out-of-trim condition (in relation to weight distribution) detected on the ground?
My question relates to Captain reports Out of trim
and
this answer.
How is an "out-of-trim" condition like the one mentioned in the linked question detected on the ground? I.e "out-of-trim" in the context of weight distribution or balance of the aircraft and not control surface trim.

Related: Is passenger weight distribution important on a commercial flight?

Most likely there was a last minute passenger and/or cargo adjustment.
One checklist item to be done before takeoff is setting the elevator trim. For this, you plug in the numbers (weight of each cargo section + passenger section + fuel), then the computer will tell you the trim value.
Of the entire trim range, only a portion is valid for takeoff. Say the range is 0-10, but you can only takeoff with the trim set between 6-8.
The pilot input the numbers and found the result to be outside the permitted range for takeoff.
In case you are wondering, there are no weight sensors on the gears. On the ground, Weight & Balance is calculated, not measured.

The most likely scenario, where you have an unforeseen deviation from plan at the last minute, is pax loading where due to a statistical fluke there is an uneven distribution of pax in the cabin, say because a lot of them didn't show up and the no-shows tended to concentrate toward one end.
When the FAs inspect the cabin after boarding, they do a pax count and one thing they are looking for is a minimum number of pax in each cabin weight and balance zone.  If the FA sees something that is out of whack, like the front half of the cabin near empty with a crowd at the back, they will let the Capt know, and if necessary will start going around to pax to request them to change seats to address the under filled zones.
For cargo, the crew has to trust the people that loaded the cargo weight and balance wise.  For fuel, it's mostly about making sure the fuel load indicated in the cockpit matches the fuel load paperwork and the weight and balance load sheets and trip requirements.
In a line operation, the crew doesn't have to do any of the actual dirty work, they are just presented with the information prepared by specialists and review it to make sure it jives with expectations and requirements.


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IDLE Factor determination
The Flight Management System (FMS) utilises the Idle Factor to modify the computation of the vertical profile whilst descending.
During this phase, the FMS calculates the vertical profile and predictions from the Top of Descent (TOD). Depending on the value of the IDLE factor, the FMS modifies the position of the TOD and computes a vertical profile based on the given thrust (IDLE + DELTA). Therefore, the IDLE factor has a direct impact on the computation of the vertical profile and the aircraft's ability to maintain the vertical profile.
Does anyone have practical advice for determining the appropriate idle factor value (what parameters to look at, how to analyze them, etc.)? Providing learning materials or resources would be appreciated, as I do not want this to appear as homework assistance.
P.S. English is not my first language. I hope my question is clear.

Are you working on writing FMS algorithms? What is the reason you need to determine this value?

@RalphJ Airline flight ops departments may need to update the IDLE factor as the engine ages and is replaced. Certain mods and aircraft operating conditions, like galleys and IFE that draw large electrical currents, will affect IDLE. Getting the FMS predictions right will save fuel.

@user71659 Okay, is that what the OP is working on? Because if so, I'd expect that the engineers there might already have some resources, and if they don't then the manufacturer of their aircraft surely does.  How much data and knowledge is the OP starting out with?  Needing to write a first cut at hypothetical parameters for generalized software is a whole different challenge than taking existing parameters and adjusting them for a particular change, and giving us an idea of what stage of the problem he's at may help the OP get a better answer here.

@RalphJ The reason for the Idle Factor determination is proper fuel prediction and adjusting the Top of Descent. Refer to the video: https://www.youtube.com/watch?v=KAeL7ekh7jQ. The video says that Flight OPS team is the one to determine the Idle Factor, but the only solution they mention is outsourcing this through Navblue or other services. At this stage I am just trying to understand how this works as nobody in my company knows and never did this before.


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Dispatch Landing vs. Inflight Landing Performance Calculation
What is the difference between Dispatch Landing and Inflight Landing Performance Calculations? Are you obliged to use both? Specifically concerned with EASA rules.


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Why is higher V1 preferred over lower V1 in takeoff performance calculations?
I am using a takeoff performance application that seems to prioritize a higher V1 speed whenever there is extra runway available. It does this as long as the Acceleration-Stop Distance (ASD) remains within the runway limits. I understand that V1 is the critical speed below which a takeoff can be rejected and the aircraft can be safely brought to a stop within the remaining runway distance. However, I am curious to know why a higher V1 is generally considered better than a lower V1.
Intuitively, it seems like a lower V1 would allow for a shorter ASD, which would be advantageous in terms of runway usage. Is there a specific reason why higher V1 speeds are preferred? Are there any safety or performance benefits associated with higher V1 speeds?
Additionally, are there any drawbacks to using a higher V1 speed? Could it compromise safety or lead to any operational limitations?
I am trying to understand the rationale behind the computation of V1 in this context as well as the implications for takeoff safety and performance. Any insights or references to relevant guidelines/regulations would be greatly appreciated.

It depends on whose point of view. From an engineer's POV, lower V1 (in relation to Vr) improves the takeoff field performance, which in turn makes the plane more enticing. From a pilot's POV, given a fixed runway distance, higher V1 means the abort can be delayed as much.

To amend John K:s answer, choice of V1 is basically matter of two things: do you want to minimize Accelerate-Stop distance or Continued Takeoff distance in case of engine failure. By choosing low V1, there will be more runway available in case of engine failure but as described by John, in case of an engine failure just above low V1 you still have to accelerate to Vr and then carry on towards V2 before runway end. Also if there are obstacles beyond end of the runway low V1 will put you closer to the obstacles as acceleration from V1 to V2 is lower with single engine.
High V1 increases the Accelerate-Stop distance, but shortens the takeoff distance in case of engine failure, leaving more runway to to rotate and leaves more room regarding the close-in-obstacles.
The only reason I would see to choose lower V1 is if runway is contaminated to the extent that you are doubtful if you would actually achieve reported braking action. Especially the very end of an icy runway tends to be more slippery than the average, reported runway condition. Then again, I wouldn't go to close to VMCG (minimum control speed on ground) either as it assumes dry and calm conditions. Should engine failure occur there, the controllability on ground might become an issue.

Generally you want the decision speed V₁, above which you are supposed to carry on and fly no matter what (with rare exceptions), as close as possible to rotation speed. That is, preserve the ability to remain on the ground, if something goes wrong, as late as possible without running off the end, to minimize the potential rolling acceleration phase that has to be done with a dead engine.
To visualize, take it to an extreme. V₁ is a function of accelerate/stop. Say that because the brakes on your plane were a very poor design so you needed a LOT of runway to stop on a rejected takeoff, so bad that V₁ had to be set at 100kts to be able to reject and stop in time on a given runway, with a rotation speed of 150kts.
An engine quits at 110kt, well past V₁ and because of that you have to keep going and take off because of your crappy brakes. But rotation is at 150, so you have to sit there accelerating to rotation speed for an eternity with one engine surging or vibrating or on fire. So V₁ will be set to the highest speed that allows a safe stop following a reject, to minimize the rolling acceleration phase to rotation, and you only reduce it because a short runway or degraded runway friction or some other parameter forces you to.
At whatever speed that is set for V₁, a number of allowances or fudge factors are built in, such as an assumed delay on getting on the brakes, to ensure the calculated stop distance can be achieved. A high energy reject like that is considered high risk, but still less than the risks built into a single engine takeoff, so if you can stay on the ground and stop, you stay on the ground and stop.
On the flip side of that, once past V₁, stopping on the runway is no longer a consideration, and you can actually take your time rotating. Inexperienced pilots can think they need to get in the air as fast as possible at Vᵣ with the end of the runway looming, and can tend to over-rotate by rushing the rotation.


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Minimum Safe Altitude vs Emergency Safe Altitude
Is there a difference between Minimum Safe Altitude and Emergency Safe Altitude? Or are they same things used by different authorities (MSA by EASA and ESA by FAA)?

Are you sure EASA uses MSA for "Minimum Safe Altitude". All I could find was "Minimum Sector Altitude" (e.g. in SEAR). SKYbrary warns that this is not the same definition.

No, I am not sure. That was a guess.

Perhaps this helps - from the FAA Glossary -

MINIMUM SAFE ALTITUDE (MSA)-
a. The minimum altitude specified in 14 CFR Part 91 for various aircraft operations.
b.  Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance for emergency use. These altitudes will be identified as Minimum Safe Altitudes or Emergency Safe Altitudes and are established as follows:

Minimum Safe Altitude (MSA).
Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility, waypoint, or airport reference point upon which the MSA is predicated. MSAs are for emergency use only and do not necessarily assure acceptable navigational signal coverage.

Emergency Safe Altitude (ESA).
Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance in non-mountainous areas and 2,000 feet of obstacle clearance in designated mountainous areas within a 100-mile radius of the navigation facility or waypoint used as the ESA center. These altitudes are normally used only in military procedures and are identified on published procedures as “Emergency Safe Altitudes.”


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what would couse uneven fuel levels in a cessna 207?
I have problems whit the level in each tank after a flight of 3 hours. I usually use the right tank the first hour and then I change to the opposite, but when I check the level after that the rigt tank seems as if have not burned the fuel.

Is your right tank fuel gauge working?

yes, it is working my friend.


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Advantages and disadvantages of air intakes above fuselage/wings in jet fighters?
I found some jet fighter designs that never went into production. All of them have air intakes above the fuselage or wings (albeit not in the same manner).

I'm trying to assess if there'd be any point in making planes like those.
There are almost no real-life examples of small planes with similar placement of air intakes, so maybe it would be too disadvantageous? I know only of A-10 and F-117, but they are both ground attack aircraft. Some say those designs would be prone to engine failure while doing sharp maneuvers with high angle-of-attack in a dogfight. On the other hand, isn't air travelling faster above wing/fuselage?
What do you think? Would there be any point in manufacturing planes like this in real life?

Russian planes flying from rough fields used above wing air intakes to help with FOD if that helps.

Advantages of overwing intakes:

Little danger of foreign object damage (FOD). Remember that F-16 bases need to keep their runways spotless in order to avoid FOD. The low intake will hoover up all loose items around it while the overwing intake mainly sucks in air from above.

Disadvatages of overwing intakes:

Lower pressure recovery at high speeds. The air above the wing is first accelerated in order to create lift and then this accelerated air must be decelerated for maximum pressure recovery. This is less direct and incurs more losses than low intakes which operate in pre-compressed air.
Operation in low density air in supersonic flight. Especially when thrust is needed most, at high angle of attack, an overwing intake will feed the engine with lower pressure and lower density air, reducing the available thrust.
Noise: The North American F-107 was said to be the loudest aircraft from the pilot's perspective, and cockpit noise was one reason why it did not enter production. Granted, here the intake was not over the wings but on the upper side of the fuselage, right aft of the cockpit, but I thought I include this item here nonetheless.

Early stage of F-107 development (picture source), at this time called the F-100 B, but the low intake interfered with weapons release from a central belly bay …

… and that is how it turned out eventually with the re-located intake (picture source)

It is possible (but I am not an expert) that in the event of a stall or certain angle of attack, the flow to the intakes could be blocked, which might be dangerous.
https://i0.wp.com/www.spacesafetymagazine.com/wp-content/uploads/2011/10/1000px-StallFormation.svg_.png
I'm inferring this from the "deep stall" that aircraft with T-tails can experience:
https://i1.wp.com/www.spacesafetymagazine.com/wp-content/uploads/2011/10/1000px-Deep_stall.svg_.png
However there is and advantage from putting engines above wings: the Coanda Effect. The Antonov An-74 takes advantage of this.
https://upload.wikimedia.org/wikipedia/commons/0/09/An_An-74TK-200_of_IRGC.jpg


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E class airspace(transition area)

Extension area(E airspace) shown as shaded magenta start from 700AGL but how to measure 700AGL over the water like in this picture?
Cuz there’s no land…

The Class E extends lower than you might think, because you need to measure from the underlying sea floor.  (Joke -- )

While the documentation uses AGL when talking about class E airspace the chart legend uses the slightly different phraseology of

above surface level

This avoids the ambiguity of, ground or ocean.
Interestingly the glossary uses both ground level and sea level but explicitly defines neither.

Now I get it! Thx for your explanation.

When you are over the water that’s actually the easiest to measure. If you are over the water 700' AGL will read 700' on your altimeter. It’s when you are over land that it gets harder.
If you fly with something like ForeFlight you can set one of the display boxes on the bottom of the screen to show height above terrain, but otherwise you just have to use your judgement.

Nit: That should say over the "ocean". Lakes and rivers inland (also "water") can be much higher.

@StephenS True, but in his example water and ocean are the same thing.

Looks to me like the chart is showing controlled airspace as 100/60, 100/50, 100/40 -
which means the highest you can go is 4000, 5000, 6000 feet MSL and stay clear of the Class C, not AGL. So the height would be read off the airplanes altimeter.
Go to www.skyvector.com, enter HAF at the top left, then select San Francisco.  To the left of HAF is the explanation showing T/30, and 70/30 - in MSL.

You misread the chart. Starting at the inner ring the Class Bravo starts at 4000 and goes up to 10000 MSL, then 5000MSL, and then 6000MSL.

Yes, you're right. Updated my answer.


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Black aircraft at night no lights with helicopter following - is this a stealth aircraft?
I have just seen a dark long aircraft fly over my car followed by a long helicopter. I am not an expert at this but it is 8pm, i am on a hill with a few houses, there  is a little street light on the clouds, The clouds are not too high or too low and are broken allowing some stars through. I was sitting in my car listenin to music when I heard a helicopter quite low and loud sounding. Not unusual as we have a police helicopter out a lot and we are near Lympstone Commando base In Devon.
I looked up through the window and saw a long black aircraft fly quite fast 50-90mph? But it had no lights on at all. It looked like a shadow but it blocked the stars as it went past. Then 2-3 seconds later a helicopter passed, a but further away going the same direction, Almost like it was escorting it?  This helicopter had a light flashing at each end but it must have been huge. Army for sure I should think. I only heard one helicopter - but i was in the car with some music one to begin with. But my question is no doubt it is an aircraft but what aircraft would be allowed to have no lights on at night? Or do you think I was under the belly of a military helicopter and just couldn't see the lights?

80-90mph would be incredibly slow for a stealth aircraft of any kind, if that is truly the speed you believe it was going, it would be something different.

Hi thanks for the response. Like I say I cant really tell the speed not being an expert.But it took about 3-5 seconds to pass across my line of vision and from where I was sitting the angle I suppose would be 50 degrees. from my car to the craft.  So it seems likely to be another Helicopter? But not sure why the lights would be off.

@RonBeyer: That's why they were using a helicopter as a chase.

It's likely not a stealth aircraft due to the speed it was flying at. Your speed estimate of 90mph is unrealistically slow, particularly for military aircraft. However, here is the likely scenario:
You misidentified the aircraft: At that speed, or anywhere near that speed, it was likely to have been a helicopter. In the world of VTOL and Tilt-Rotor aircraft, which private and military industry are both pushing heavily, these are becoming more and more common. In fact, the United States Marine Corps trains quite often with the Royal Marine Corps - and we have tiltrotor aircraft! The MV-22 Osprey, pictured below, looks like a plane, but tilts its rotors to achieve a helicopter-like flight model. And let me tell you, these are loud and sound exactly like helicopters. They're also quite big, and will look doubly so when flying low over your head.

In the United States, our military do so-called "dark" flights quite often. They're practicing the skills required for these flights, and it is perfectly legal for them do so, with the proper safety precautions.


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Since speed is related to dynamic pressure, then why is static pressure used instead of dynamic pressure in ASI to measure speed?
Since speed is related to dynamic pressure, then why is static pressure used instead of dynamic pressure in ASI to measure speed?
Why is dynamic (or pitot) pressure not sufficient?

What you have in mind is a pitot-static tube aka Prandl tube, a sensor delivering the stagnation pressure information. For the simple Pitot tube, we need the static port information. Difference.

Since speed is related to dynamic pressure, then why is static pressure used instead of dynamic pressure in ASI to measure speed?

It's not. The reading on the airspeed indicator is directly determined by the dynamic pressure. The ASI uses the static pressure for the sole purpose of determining the dynamic pressure.

Why is dynamic (or pitot) pressure not sufficient?

Dynamic pressure is sufficient, but the pitot tube doesn't give you the dynamic pressure; it gives you the total pressure, which is the sum of static pressure and dynamic pressure. In order to determine the dynamic pressure, an airspeed indicator has to find the difference between static pressure (from the static tube) and total pressure (from the pitot tube).

The ASI uses both, dynamic pressure from the pitot tube, and static pressure from the static ports.  If just dynamic pressure was used, then at some point the system becomes pressurized and no change is seen. Having the static ports involved introduces effectively a controlled leak so that changes in dynamic pressure can be seen.

Source: https://www.skybrary.aero/index.php/File:Pitot_Static_System.jpg

Your second sentence is not correct.  If you seal the static port, then the ASI will still work correctly for a single altitude and barometric pressure.  But, will be wrong if either of those change.  Essentially, the static port acts to calibrate for changes in pressure.

And how useful is single altitude/barometric pressure?  Not at all. That is why planes have multiple exterior static ports (my plane has 2 for instance, one on each side of the fuselage), and if those should become blocked (ex. taped over for washing and then not uncovered - reference the airliner that crashed off the coast of Brazil I believe) there are alternate static ports inside the plane that can be used.  Data will not be as accurate (as the port is inside vs being exposed to external air), but it's better than nothing.

"dynamic pressure from the pitot tube" - Doesn't the pitot tube give total pressure, not dynamic pressure? That's why the airspeed indicator needs to know the static pressure as well. If the pitot tube gave dynamic pressure, then the airspeed indicator could be connected to only the pitot tube and not the static port.


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Do sectional charts indicate which runways have lighting installed?
KSFF has 3 runways (one in the water, two on land).
The sectional shows *L yet only 4L/22R has lights. Is there a trick on the sectional to tell which runway has lighting or do you have to look at the supplement?

There is no way to tell which runway is lighted from the sectional chart.  You have to check the Chart Supplement. From the FAA Chart Users' Guide (27 January 2022) p. 16:

The lighted runway may not be the longest runway available, and lights may not be illuminated along the full length of the runway. The Chart Supplement has a detailed description of airport and air navigation lighting aids for each airport.

@ymb1 - nice addition, thanks


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Why do pilots normally fly by CAS rather than TAS?
I think I know the answer to this question, but I want to confirm. Airline pilots normally fly a CAS/Mach profile, which means that above the CAS/Mach transition altitude they fly by Mach, and below it they fly by CAS (calibrated airspeed). Why do they fly by CAS rather than TAS (true airspeed)? My guess is that they use CAS because that is what their airspeed instruments show naturally, whereas TAS requires computation to determine. Is that right? Or is it also because it helps to slow down in descent and speed up in climb (since a constant CAS in climb corresponds to an increasing TAS)? Thanks.

I think you mean Indicated Airspeed (IAS)—not Calibrated Airspeed (CAS). The airspeed that shows up on the indictor is Indicated. At very low airspeeds with gear and flaps extended it often varies from Calibrated Airspeed (CAS) and there are tables that show the corrections. https://aviation.stackexchange.com/questions/41030/how-are-ias-to-cas-conversions-calculated

No, I meant CAS, not IAS. I believe CAS is just IAS calibrated for instrument error. CAS is what pilots usually fly to, not IAS.

Could you provide a source for that statement. As a general aviation pilot, I fly by what is on the airspeed indicator. If I want to know the calibrated airspeed, I have to look it up in the POH. At cruise speed, CAS and IAS are the same for the airplanes I fly. They only differ in the landing configuration. My understanding of the guys that fly the big jets is that they too fly by what is indicated e.g. 250 kts max below 10,000' etc.

I am not a pilot, and I don't know much about GA, so I should have stipulated that my comment applies to commercial airliners. "CAS/Mach profile" is a commonly used term, but I have never heard of "IAS/Mach profile." I assume that's because airliners have sophisticated enough avionics to automatically apply the correction to IAS to compute CAS.

The reason is somewhat deeper than just the indication. Up until Mach-related effects come into play, CAS is what the airplane 'feels' as speed, and consequently, is all the pilot needs to know. The TAS, or even better, ground speed, is needed primarily for navigation, but not for flying per se.
All the most important aerodynamic quantities (lift, drag, moments, etc.) are proportional to dynamic pressure:
$$q = \frac{\rho V^2}{2}$$
where V is TAS. So apart from TAS, they all depend on the ambient air density $\rho$. CAS is, essentially, TAS 'corrected' for the factor $\sqrt {\rho / 2}$, i.e. the effect of density. Instead of two parameters now you need one. But it doesn't mean CAS is calculated from TAS; rather the opposite: it is easier to naturally measure CAS (or q), and hence it is displayed (becoming IAS). To get TAS, you need to measure $\rho$, which is normally done via known pressure altitude (i.e. static pressure) and temperature.
If you climb at a constant CAS, your TAS will increase as the air becomes thinner ($\rho$ falls), but most importantly, the airplane handling qualities remain largely the same. But at some point, you'll hit the Mach limit and will have to obey it. Technically, the transition is governed by Mach itself rather than the altitude.

Interesting. So constant CAS means essentially constant dynamic pressure (until the Mach number gets up to the point where compressibility effects come into play). Since a pitot tube measures dynamic pressure, that makes sense. Thanks!

Yes if you stuck your arm out the window at 200kt indicated at sea level and at 200kt indicated at 40000 ft, the force trying to bend your arm back would feel the same even though you are moving twice as fast.

Indicated Airspeed, IAS, is a measurement of the relative pressure caused by resistance of the air moving forward.  It is what is directly measured by a pitot tube referenced against a static port on an aircraft.
Calibrated Airspeed, CAS, is the adjustment of IAS for instrument error.  Not everything is perfect, and pitot/static systems have errors.  Consider when engaged in high alpha (high angle of attack) flight, that there may be less "area" of the pitot tube facing into the relative wind, resulting in a lower IAS than would be detected by a perfect airspeec indicator.  With computer systems it is easy to utilize flight parameters to create a display of CAS, rather than IAS, so CAS is used in some aircraft.
True Airspeed, is airspeed adjusted for atmospherics, so that the airspeed corresponds to the ground speed in a no-wind situation.  This adjustment is primarily based upon altitude (absolute air pressure) and temperature.  Secondary effects include humidity.
While TAS corresponds to a true speed in the air, it is not a strict measure of molecules of air going past lifting surfaces the way that CAS is, and therefore, is not useful in safety of flight issues, such as landing speed.  CAS, being a calibrated (adjusted for instrument error) measurement, effectively provides the number of molecules passing by in the relative wind, and is therefore the measurement best suited to provide safety of flight information such as landing speeds.
Hot temps, and high altitude, will result in higher TAS for the same CAS.  CAS will effectively predict aircraft handling characteristics, such as lift.
Simply stated, TAS is for navigation and flight performance, and IAS/CAS is for conducting flight operations where the effect on the airframe is being utilized.
Disclaimer: This discussion is directed at subsonic flight, and does not address the effects of air compressiblility.

"TAS... it is not a measure of molecules of air going past" - in some ways it is: it determines the time it takes for the molecules to pass the wing. This also matters, in particular for aeroelastic effects (flutter) and everything determined by the Reynolds number. TAS is just not a measure of the impulse exchanged between the wing and air.

It’s been a while, but my recollection is that sophisticated aircraft systems provide a correction for installation and configuration-induced errors, so that the pilot is shown CAS, not IAS. You are not likely to encounter these systems in GA.  My experience is F-4s and F-15s. That is likely why Russ has seen reference to a CAS/Mach climb profile for airliners.

Welcome to Aviation.SE! The question was why TAS is not used (when available), not about IAS/CAS difference. Maybe you can add something on that? Also, many GA aircraft built today have glass cockpits with ADCs (air data computers) for these calculations.


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How is the change of moment handled in a Weight and Balance calculation with a swept wing aircraft?
I'm writing a weight and balance calculator for a charter operation.
Every aircraft I've ever flight planned for has all the tanks on the same moment arm, so I don't know how you calculate the W&B for an aircraft that has swept wings. Do they have one tank on each wing whose moment changes as it drains, or do they have multiple tanks? And if they have multiple tanks, so you have to calculate for 'drain the forward tanks first' and 'drain the rearward tanks first' and plot both of those on envelope?

Most twin engine jets have one very long tank in each wing for each engine and often a center tank that feeds both.  The fuel shifts forward as fuel is consumed from the wings (dihedral plus sweep), and aft as fuel is consumed from the center tank, if installed (always before the wings, so if there is a center tank the C of G moves aft until the tank is dry and forward as the wings are consumed).  The manufacturer's weights engineering group will determine the overall fuel load's center of gravity moment for different fuel volumes and plot the results on a chart as a curve.
When you do the load sheets on a swept wing airplane the fuel moment/mass curve will be integrated into the chart data so that an accurate fuel moment/mass value is applied to the C of G calculation for takeoff.  Also, some form of the fuel curve will be overlaid onto the C of G limits chart to confirm that the C of G shift will stay in limits as fuel is burned during the flight.  This is especially important for jets with center fuel tanks, because you may be able to load it with a marginally aft G of G, such that the aircraft is technically in C of G limits at takeoff with a full fuel load, but as the center tank is burned off the C of G could move past the aft limit temporarily until some of the wing fuel is burned off.  The result is the C of G with center tank at zero will determine the aft limit for freight/pax.

That's what I was wondering about. With all the tanks on the same arm, I put 4 points on the CG envelope chart - full fuel, take off weight, landing weight and zero fuel weight, and a straight(ish) line between them. I was wondering if I'd have to have more like a diamond with full fuel, empty this tank first, empty that tank first, empty the center tank first, etc.

You don't need 4 points, you just need to know the overall moment for the combined fuel tanks with whatever quantity is on board, which will be with the CG data for the airplane.  The only real difference is that the moment changes as fuel is burned and that has to be taken into account.

Sorry to come back this after 2 years, but the guy I was writing the W&B calculator for didn't buy the Challenger after all until recently, and so I'm revisiting this. And while he hasn't sent the the relevant pages of the Challenger W&B Handbook, I found this graph online, and it shows a curve. https://code7700.com/images/cl-605_weight_and_balance_chart_example_2.jpg. I assume the three straight segments are center line tanks and the curve is wing tanks? What determines the formula for that curve?

The chart indicates there probably an aux tank forward that gets burned first, the first zig aft, then aux tanks aft (saddle tanks back around the baggage area and I think they can also come with a tail mounted tank), the second zig sharply forward, then the center tank,  the third zig aft, then the wings, the curve.  The curve is a plot of the depletion of the fuel volume's C of G as its depleted, and the shape of the curve will be a function of the slope and contours of the tank bottom and fore/aft spars.  You'd have to be able to model the fuel tank space accurately to work it out.

In supplement to @Dave's answer and as he said depending on the airplane, the complexity of calculating the c.g. can vary greatly. The manufacturer of every large aircraft I've programmed weight & balance for has had tables for each tank. In Boeing's case for the 747-400, each table line is a tank volume in gallons and the tank c.g. at that volume in inches. For example, and using JSON notation since the OP is JavaScript fluent:
{"vol":3200,"ba":1453.7},
{"vol":3250,"ba":1454.8},
{"vol":3300,"ba":1456.0},
{"vol":3350,"ba":1457.2},
{"vol":3400,"ba":1458.4},
{"vol":3450,"ba":1459.7},
"vol" is the fuel volume in the tank in gallons
"ba" is the balance arm at that volume in inches
Since fuel is loaded by weight, one has to use the fuel density to convert to volume.
Typically, at least for large aircraft, you have to satisfy the c.g. envelope for:

zero fuel weight
ramp weight after fueling
takeoff weight
landing weight

Also there has to be provision for carrying ballast fuel if that is necessary.

You will need to consult the POH for the airframe in question and see what it says in regards to fuel burn from tanks at different moment arms. Ultimately you will need to program in the variable factor of fuel burn. It sounds like the program will have more inputs than just the weight of the passengers, fuel, and cargo. The end user will also need to input their planed fuel burn schedule and the order of the tanks they intended to burn off of. Once you have all this info you can compute inflight CG at different times. What you are going to end up with is a piecewise system that describes your WB at various points in the flight.
One of the contributors here @Terry built a WB app for some 747 variants that he used when he flew. You can find it here, it might be worth reaching out to him if he does not add an answer here.

+1 for mentioning @Terry's site. (Not that either of our @ references will notify him...)

@FreeMan We should suggest that @Tagging work in posts and comments, it would be a nice feature (although I can see it getting out of hand in some cases) and opening up more "discussion" style answers.

@dave there are already questions about that on MSE and I take it it is by design that @replies are working only in comments. There is not even a simple way for this to work as is since usernames are not unique - there are at least 16 Dave's on Aviation alone.


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Are there any photos or videos of the drones at Gatwick?
The Gatwick Airport drone incident from 19-21 December 2018 involved "67 reports of drone sightings close to the runway" (Wikipedia).
However, police stated there were no photos or videos of the drone (The Guardian, 23 Dec.).  Later, police said that statement had been the result of "poor communication" (The Guardian, 24 Dec.).
Regardless, I haven't found any photos or videos of the drones.  Are there any?  If not, why not?  Were they too small (or far away) to be seen by a cellphone camera?  But then how could humans see them?  How can 67 people see a drone in this day and age and none of them record it?  Is it plausible that there actually were no drones?

There’s a picture here: https://www.dailystar.co.uk/news/latest-news/749188/breaking-gatwick-airport-drone-picture-easyjet-delays-flights-cancel-compensation-travel/amp but the twitter account it was originally posted on seems to be down, so not sure how valid it is. But it’s definitely difficult to take a picture of a small moving drone from a distance.

An “unverified” video (difficult to say this was even at Gatwick): https://news.sky.com/video/gatwick-drone-caught-on-camera-in-unverified-footage-11587927

The Wikipedia page on the event says:

No videos or photographs of the drone were handed to the police.

The New York Times also says there is no solid evidence.
Despite multiple eye witness accounts, no photos or videos of a drone exist.

The question is: Are there any photos or videos of the drones at Gatwick?.  The answer is clearly, "No, there are not" (regardless of what the cops might believe).

OOI why did you post another answer rather than just update your previous one?

Here's an archived copy of the 2019-02-21 Reuters article.  The ban on mobile phones at ATC is interesting as it explains one reason why there are no photos or videos.

It is very likely that there were no drones, and this was a case of mass hysteria.
One actual crashed drone was discovered during the search, but that could very likely have been a hobbyist drone that got away, days, perhaps weeks earlier.  Lost toy drones happen all the time (even though it shouldn't happen near a major airport, it does...)
https://www.secretflying.com/posts/police-admit-it-is-a-possibility-there-was-never-a-drone-at-gatwick-airport/

-1 You need a better source than a discredited police report


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Aerodrome category, certification?
I need to know how you tell the certification of new airport just built? how can you tell if airport is certified for International flights or not? approved for intl flights or not meeting requirements?
I find this recent airport in Egypt HESX with regional flights approved, yet it has no lights and it operates only during day time, so is it approved for intl flights or not?
Sphinx Airport Map

For what it's worth, HESX is adjacent to and shares infrastructure with the Egyptian military's Cairo West Air Base, which has been a destination for international flights for years. I took U.S. troops in and out of there from and to the U.S. in the 1990s. The flights were always during the day, never at night. We always assumed, whether correctly or not, that the military wished to keep the base dark at night to make it more difficult to find and attack.

Thanks Terry for your input, yes i understand its shared airfield, Egypt is opening up new regional hubs taking advantage of per-existed military airbase, i just find it very weird the new expansion is too small to accommodate intl operations, few taxi ways, 24 m width which wont be able to receive wide body aircrafts, limited bay etc...no cat2 or cat 3 .... knowing the civilian section wont use same rwys as military ones, and i believe with now days technology its bit stupid not to have lights on to avoid detection :) specially for civilian operations. i cant find zaairport category anywhere

Some information specific to taxiways in ICAO Aerodrome Design Manual, Part 2 p9. (runways are in part 1)

Your question is a bit unclear. Any airport can be used for an international flight. Do you mean commercial airline scheduled service? Also, there is no requirement that an airport be open at night for it to host commercial scheduled airline flights, domestic or international.


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What weather should we expect when temperature and dew point are similar?
What should i expect during my flight planning when i see both temperature and dew point are the same?
I understand there will be fog but what else? could it mean icing? any difference between 20/20 and 04/04 for example to expect?

You think you’ll get icing at 20° OAT?

@Arkhem - Possibly once you are nearing 10,000 feet AGL. Remember that the temperature on METARs and TAFs is in Celsius.

@DeanF. 20° at 10k still wouldn’t be freezing. Unless you’re doing 2° per thousand feet at which case it wouldn’t be 20°...

@Arkhem - Since a METAR or TAF would be giving the temperature at the surface, a standard lapse rate of 2°C per thousand feet would put you at “freezing“ at 10k’ AGL. The OP did not specify that he was getting his temperature and dew point from a Winds/temps aloft chart or a skew-t/log-p diagram.

So we’ve established that when it’s freezing outside you’ll get icing... how does this relate to it being OAT 20 and dew point 20 on the ground and it not being in icing? Your comment seems irrelevant

Both 20/20 and 4/4 will probably result in fog or thick haze/mist.
4/4 is a problem because it tells you that besides the airport being likely fogged in, the freezing level is only a couple thousand feet above the airport and there is very likely icing at that level if there is any cloud up there. Only airplanes capable of flight in icing would be coming and going, if at all, depending on the actual runway visibility.
20/20 is also likely fogged in, but the freezing level is up at 10000 ft so that's not a problem.  15-20C is a sweet spot for carb icing, so saturated air at that temperature is a major concern.
The other thing to take into consideration is temperature tendency.  Generally, a zero spread like that in the morning means you can expect to wait a couple hours and the fog will lift.   On the other hand, a spread approaching zero in late afternoon is a big red flag.
When I was bush flying on floats in Northern Ontario, the dew point spread was the most important bit of data when checking weather.  A spread of one degree in the morning when departing on a trip was no worries because it would only improve (absent frontal conditions etc) as the day warmed up. On the other hand, a tight spread in the afternoon might mean making a customer wait at the lodge until the next morning rather than risk getting caught out scud running home at 500 ft, with clouds forming all around as the spread became zero, necessitating a diversion to the nearest lake on the route.

As a very practical rough guide with a stable air mass at sea level, for every degree the dew point is different from the air temperature (in degrees C), the cloud base will be approximately 400feet. Eg 7/5 = 800ft in the lower levels.

Close temperature and dew points will mean the possibility of visible moisture. Fog is one aspect of that. At 20°C, structural icing is going to be rare below 8,000 feet AGL. On the other hand, Induction (carburetor) icing on low power settings with rich mixture settings is very possible. At 4°C, beware of structural icing as well as carb ice.


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VOR GND Receiver checkpoint
KEUG currently has the following NOTAM
!EUG 02/045 Mahlon Sweet Field, Eugene, OR (EUG) Navigation VOR ground receiver checkpoint unserviceable Feb 15, 2024 1750Z (10:50 PDT) to Mar 21, 2024 2000Z (13:00 PDT) Estimated
Does that mean they cannot receive communication on VOR in case of lost comms? Is the VOR otherwise functional?

A VOR ground receiver checkpoint is a place on the ground where you can check that your VOR receiver is working correctly. This NOTAM means that you can't use it. It has nothing to do with air navigation or lost communication procedures.
The VOR should otherwise be working properly, absent another NOTAM to the contrary. It's likely that construction is interfering with the signal at the checkpoint or something like that.


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Bottom of class C vs top of class D
When a top of class D ([45] on the chart below) conflicts with bottom of class C (37) which prevails?

AIM 3-1-3 answers this:

Hierarchy of Overlapping Airspace Designations
When overlapping airspace designations apply to the same airspace, the operating rules associated with the more restrictive airspace designation apply

More details are given in this answer about the big bravo across the state.

@757toga you might have to edit my answer to explain/correct it. I don't see how the Delta applies- as the linked answer says, 2200 feet over I-90 is in the Bravo, not the Delta. 7400.11F has rules from 1994, the second one (pg D-72) says ".. excluding that airspace within the Seattle, WA, Class B airspace area."

This is more a “thought exercise” question than one that’s likely to present a real-world quandary.  The two controllers are in near constant communication with each other and have probably worked together every day for a long time.  The two facilities will have memorandums of understanding about how to handle various situations, that you’ll probably not know of.
As a general rule, if you are taking off you’ll be talking to the tower (Class D) first, and they will know when to hand you off to the Class C facility.  If you are arriving, you’ll be talking to the Approach facility (Class C) first, and they will know when to hand you off to tower (Class D).  If you were approaching the airport in your chart fro the east, you could contact approach several miles before getting to the east border of the Class B.  They usually welcome arriving traffic to contact well beyond the magenta rings.  Or, you could contact tower before crossing the east boundary, because if you were landing, you’d most likely already be below the Class C floor well before reaching the arrival airport.  So either is perfectly legal.
Perhaps the most common driving factor is whether you need radar navigation.  The Class C has radar and the tower may not, so generally the agreement is that the Class C controller will stay with you for as long as you need navigational support.  If you can’t find the airport, they won’t hand you off until you do, and they will take responsibility for coordinating with tower until you are handed off.  If the Class C controller is saying “Airport 11 o’clock 6 miles”, they’re hinting that they are ready to hand you off.  If you say “Airport in sight”, they’ll almost always hand you off right away, even if slightly outside the D because they have radar visibility into anything between you and the airport.
In my experience, the Class D space tends to “win the tie”.  That is, a Class C controller will tend to hand you off before you get into the gray area of ambiguity.  Or, a Class B or C controller will often tell me I am cleared to enter into an associated Class D, and this clearance does meet the legal requirement for entering the Class D.
Astute controllers or not, there IS still a regulatory 2-way comm requirement on YOU as PIC, so if you feel like you should have been given the frequency change by now, or an explicit clearance, just ask.  Often just “Spokane Approach, Skylane 1XX, runway in sight” is a reminder to the Class C controller that it’s time to go.


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Why is carburetor heat unnecessary at full throttle?
Questions like How does aircraft design affect carburetor ice? show how carburetor mount point affects the relative passive heating of the carburetor by the engine, but I've never learned why full power eliminates the need for carb heat.
Looking at how Wikipedia depicts carb ice:

Regardless of the carb's mount point on the engine, high throttle wouldn't get rid of the ice on the throttle valve, heat generated by high throttle doesn't affect the temperature of the air flowing in.
Further, when the throttle is full open, there is a greater airflow speed across the neck of the carb and hence a greater temperature drop.
So, what explains why high throttle eliminates the need for carb heat in Lycoming/Continental engines?
Thanks!

The icing you are talking about is called "throttle ice" and actually just forms around the edges and back side of the throttle butterfly.  It's not really related to the venturi that is upstream; it's from the pressure drop caused by the restriction of the throttle plate (the high vacuum on the back side you might say) along with the presence of vaporizing fuel, which massively boosts the temperature reduction caused by the pressure drop because the evaporating fuel is absorbing a lot of heat from the air stream.
It's the temperature drop from this pressure drop at the butterfly, plus the effect of evaporating fuel, that turns ambient humidity into carb ice.  On a fuel injected airplane you only have the butterfly valve without fuel present, and the temperature drop from that alone isn't sufficient, and therefore you don't need carb heat on injected engines (just an alternate air source in case of impact ice on the air intake).
Anyway, when the throttle is wide open, the pressure drop downstream of the butterfly caused by the throttle restriction is minimal. As a result, the chilling effect of the pressure drop and of evaporating fuel is also minimal. Because of this you won't get ice formation as readily (not impossible, just relatively unlikely) when the passage has say only a 5 or 10% restriction at WOT, vs say, an 80% restriction at a low power setting.  For a given ambient temperature/humidity, carb ice always forms more easily the more the throttle is closed.
One of the worst airplanes for carb ice was the 65 hp J-3 cubs where the carb receives very little conductive or radiant heat from the engine due to the carb mounting and the cowl with the exposed cylinders.  Descending with the engine at or near idle on a 65 deg F high humidity evening was begging for a carb ice related stoppage, and liberal use of carb heat was advised even if there were no signs of icing.  Carb ice at WOT wasn't too much of a problem, but you can never be sure.  Always err a little on the overuse side with carb heat, especially on Continental powered airplanes which are a bit more sensitive to all this due to the way the carb is insulated from the crankcase, at least until you get to know the engine's quirks.

I agree that with throttle more open, the temperature will be higher at the butterfly than when it's only partially open. But I think your answer precludes scenarios where the OAT is around 0 and the relative humidity is high. Wouldn't carb ice still form due to the evaporative effect from the fuel? (as in the picture from wikipedia)

Even with high relative humidity the total moisture content is lower at freezing so it's not as big a problem.  The sweet spot for max icing potential is warmest ambient temperature at which ice can form (that is, the warmest it can be and still get the required temperature drop to below 32F at the butterfly) because you have the most moisture mass available to be frozen.  This in nearly saturated air in the high 60s low 70s F.  Any warmer and there isn't enough temperature drop. Or if you have a Lycoming, you almost never get there because the carb gets so much conducted heat from the engine.

@JohnK I had to read the third paragraph several times to get it due to the "a lot less" coming late in a complex sentence. I think it would be clearer to say something like "the much lower pressure drop causes ...", but I'm not sure I understand this well enough to edit it myself.

Edited for clarity.  Thanks for the input!

There is a small risk of carb icing at full throttle but it is a much narrower range of conditions than at partial throttle. Pressure drop causes temperature drop. The purpose of the throttle is to control manifold pressure, a more open throttle creates less pressure drop from ambient outside to inside the manifold so less temperature decrease. The temperature drop must also be enough to condense moisture from the air, if the dew point is much below freezing then there is no point where liquid water forms. Direct formation of ice is like snow it just gets sucked into the hot cylinders, you need a liquid droplet phase for the ice to adhere.
So with high dew point and a large pressure drop you get super cooled liquid water droplets that freeze on impact. With low humidity the range for liquid condensation is reduced and with low pressure drop the temperature doesn't drop below freezing.
Injected engines actually can develop intake ice however they do not have a venturi and without the additional pressure drop in the venturi the total temperature drop is not as substantial or it occurs in a less critical section so problems caused by icing are not as common. Venturis are more sensitive to ice as they are part of the calibrated fuel metering and mixing system. Fuel evaporation is a contributing factor to the difference in temperature between carbureted and injected systems but it is not a major factor when comparing part throttle to open throttle within a system as the mass of fuel is directly proportional to the mass of air and less fuel evaporates at low temperatures.
Also high power settings create more cylinder heat, this heat increases engine temperature and the increased temperature increases the heat transmitted to the intake components both by increased conduction through the manifold and increased infrared radiation.(proportional to the fourth power of absolute temperature[kelvin^4])

Having the throttle at full doesn't eliminate the need for carb heat. It's actually the opposite: with the throttle at full, the drop in air temperature through the Venturi is greatest, so you're (slightly) more likely to develop ice, all else being equal.
In general, he reason you're not supposed to use carb heat at full throttle is because it reduces the density of air going into the engine, so it can't produce quite as much power. Presumably you pushed the throttle forward for a reason, so reducing the amount of power right when you need it doesn't make much sense.
If you're in a situation where carb ice is a factor, then use the carb heat before you start your climb, so that you have full power available to you during the climb itself. But if you notice that your engine power has started to drop, by all means, go ahead and pull the knob, even if you're in a full-power climb.

So John K points out that the temperature at the butterfly is higher when it's full open. But my intuition agrees with your conclusion.

It's the pressure drop at the closed butterfly, not the venturi, that causes more fuel evaporation and temperature loss. At full throttle, the butterfly is open so the temperature is higher

One of the reasons for not using carb heat at full throttle is due to the increased risk for detonation due to the temperature increase and reduction in density of the air charge.


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Landing due to low fuel
If an aircraft has to make emergency landing due to critically low fuel. Who is responsible pilot or maintenance crew?

Are you adding about a specific country or regulations?

Reponsible for what?  For landing the plane?  For assigning the blame?  For taking the blame?  For making sure it doesn't happen again?  You mean who is at risk of a certificate enforcement action, or jail time, or being fired, or being fined, or not being promoted anytime soon?  Responsible in the eyes of the FAA or equivalent authority, or in the eyes of airline or the FBO renting the plane, or in the eyes of a jury when a passenger sues for emotional distress?   The question is very broad and open to interpretation.

Also maybe unforecast fog was responsible, or the enemy aircraft that shot holes in the fuel tanks!

The flight crew is responsible for ensuring there is enough fuel on board before taking off.
Further, they are required to check the fuel consumption en route at regular intervals to ensure there is enough fuel to continue. If fuel is consumed at a higher rate than expected, perhaps due to headwinds, the crew will divert to another airfield before the fuel runs too low.
Ground crews will load up however much fuel the captain tells them to. As long as they do that they are not responsible for any mishaps during the flight.

The Captain is ALWAYS responsible, even when it's not his fault.

It's his fault to have failed to check.

What do you mean by "responsible"? If Captain Bob is flying an airliner and a bulkhead explodes due to improper maintenance, in what sense and in what way is Bob responsible for this?

@TannerSwett he took off with an aircraft that wasn't airworthy. That's his responsibility, technically. In reality he'll often be cleared of blame if the problem was impossible for him to detect, but unless that can be shown he's responsible.

Is the captain responsible in any practical sense or only in a theoretical, ceremonial sense? (Like how the dollar bills in my pocket constitute a debt that the Federal Reserve Bank owes to me, but only in a theoretical, ceremonial sense, since there is no way to get them to pay this debt.)


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what is the earth resistance to be maintained while aircraft is on ground and during ground checks for military aircrafts
While aircrafts are under servicing on ground, the external dedicated earth wires are connected to the aircraft to avoid static hares effect to human beings. How much resistance value has to be maintained?.Is there any standards available for the same.

You mean resistance between the A/C and the ground? In that case, shouldn't you be asking for an upper limit, rather than a lower one (as your phrasing implies)?

For the US Navy, according to this instruction:

The maximum resistance allowable for the cable (MS27574) itself shall
  not exceed 0.5 ohms.
The cable’s operational (in use) maximum resistance shall not exceed
  10 ohms.

The difference in values corresponds to the loss of quality in the electrical contact at both ends of the wire (clips). Contacts are allowed to be as resistive as about 5 ohms. For comparison hand to foot impedance is about 500 ohms at 100 Hz, meaning the current will be 50x lower in the body than in the wire in case the aircraft is not at the potential of the ground.
You'll find a similar requirement of maximum 10 ohms in: TO 00-25-172, Ground Servicing of Aircraft and Static Grounding/Bonding from USAF.

In small aircraft, a refueling bond wire is typically clipped to the exhaust pipe, the other end of the wire presumably connects to earth ground somewhere. This dissipates any static electricity on a metal airplane and also any static that may build up due to fuel flowing thru the fueling hose.  I suspect the resistance is in the tens of ohms range or higher depending on what kind of deposits arae built up on the exhaust pipe.
You said military - they are larger aircraft, but still subject to the same phenomonem.

An old trick is to ground out the fueling nozzle to the airplane before starting fuel flow.  Static sparks can be surprisingly strong.